Scaffold frames are a series of horizontal and vertical scaffold frame members that connect together to create a raised working platform. The overall structure is supported by the vertical scaffold members contacting the support surface, such as the ground.
Scaffold frames can be constructed from tube and clamp frame members, or from system scaffold members (modular scaffold systems). In system scaffolds, the vertical scaffold members are coupled to horizontal scaffold members at a scaffold joint. A modular scaffold joint comprises a connector on the vertical scaffold member that is designed to couple or mate with a connector on a horizontal scaffold member, thereby joining together a horizontal and vertical scaffold member. Horizontal scaffold members will be referred to in general as “horizontals,” while vertical scaffold members will be referred to generally as “verticals” irrespective of the joint/connector type.
One type of modular scaffold joint uses an end connector positioned on the end of a horizontal member, where the end connector has a lip or hook section. The lip sections are designed to engage or rest on the corresponding vertical joint connector, such as an upstanding cup or an annular ring positioned on a vertical scaffold member. One such joint is disclosed in U.S. Pat. No. 4,445,307, which discloses a connector positioned on a horizontal scaffold member, where the connector has two vertically spaced hook sections. These hook sections couple with two vertically spaced upstanding cup or ring members located on the vertical scaffold member. To lock the joint in place, the connector includes a wedge that is driven (generally by a hammer) into position below the upper ring member, thereby wedging the ring against the end connector hood section, latching the horizontal member to the vertical member. This type of connector is referred to as a Safway connector. As used herein, “latching” refers to the action of engaging a horizontal member to a vertical member, where the action of latching resists dislodgement of the horizontal member from the vertical member from an upwardly directed force.
Another cup type of latching connector is disclosed in U.S. Pat. Nos. 5,078,532 and 5,028,164 and in U.S. Pat. No. 8,206,052 all hereby incorporated by reference. These patents also show an end connector positioned on a horizontal scaffold member, where the connector has two vertically spaced hooked sections that couple with two vertically spaced upstanding cup or ring members located on the vertical scaffold member. In this device, the hooked sections engage the top edge of the cup, and a pivoting member or latch, positioned on the horizontal end connector, is pivoted into position below the cup member. The latch member has a distal end extending beyond the housing, shaped to allow for placement of the distal end beneath a cup positioned on a vertical scaffold member. Hence, when latched, the cup is trapped between the hook engagement sections of the connector housing and the distal end of the latch member. The latch pivots on a pivot pin, and can be spring loaded to bias the latch into a locking or actuated position. This type of connector is referred to as an Excel connector. Single cup embodiments are also possible, such as shown in U.S. Pat. No. 7,048,093. Other cup type latching mechanisms are in the prior art, including U.S. Pat. No. 4,369,859.
Another “cup” type of latching mechanism is disclosed in U.S. application Ser. No. 11/738,273, filed Apr. 20, 2007 (hereby incorporated by reference). This application teaches a horizontal scaffold member having an end connector with two hook or engagement areas, each designed to couple with a cup on a vertical member. The connector includes an upper and a lower latch, each the respective upper and lower coupled ring or cup members. The two latches are mechanically coupled allowing for single action operation to engage or disengage both latches simultaneously. In general, a system scaffold using a cup on the vertical member with a latch on the horizontal scaffold member (whether slidable or pivotable) will be referred to as a cup/latch scaffold system. This is also in the scope of an Excel connector.
Another cup-type of latching connector is disclosed in U.S. Pat. No. 3,992,118 (commonly referred to as the Cuplock system). As disclosed in this patent (see particularly FIGS. 3 and 4 of this patent), the vertical scaffold member (generally a pipe) has a fixed annular ring 10 forming an upstanding cup surrounding the vertical member with upward facing annular channel. Positioned above this upstanding cup at a set height is a lug 20. Slidably and rotationally positioned on the vertical scaffold member above this fixed cup, is a reverse cup (a cup facing downwardly) 14 that has a downward facing annular channel, and an outward projection 18 in the cup wall that forms a slot 17. This slot accommodates the lug 2, so that the reverse cup, with the slot aligned with the lug, can slide past the lug, and if the slot is not aligned with the lug, the reverse cup cannot slide past the lug. The corresponding horizontal scaffold member (generally a pipe) has at each end, an upward facing ear or tongue 26 and a downward facing ear or tongue 27. Each respective tongue is shaped to fit in the annular channel formed in the respective upward and reverse cup. To assemble a joint, the downward tongue on the horizontal member is positioned in the upward annular channel of the upstanding cup. The reverse cup is then slid down the vertical member, past the lug 20 (by proper alignment of the slot 17), to capture the upstanding tongue within the downward facing annular on the reverse cup. The reverse cup is then rotated on the vertical member until the slot 17 is not aligned with lug 20, thereby “locking” the tongues of the horizontal member between the upstanding cup, and the reverse cup (hence the name cuplock).
Instead of upstanding cups, a flat annular ring with openings in the ring may be used as the vertical connector on the vertical scaffold member, to couple to a connector on a horizontal scaffold member. Examples of annular ring/connector systems are shown in U.S. Pat. Nos. 4,273,463; 6,027,276; 5,961,240; 5,605,204; 4,840,513; and PCT publication number WO 2011/094351, all of which are hereby incorporated by reference. These systems are generally referred to as wedge or pinlock scaffold systems. The pinlock system relies upon a wedge or pin being slidable (generally hammer driven) through the horizontal end connector and rosette. For instance, the joint of U.S. Pat. No. 5,961,240 (see FIG. 1 of that patent), uses rosette rings 16 positioned on a vertical scaffold 14 member. The ring 16 has a series of openings 22 therethrough. The horizontal end connector 10 is a body with a horizontal slot or mouth 18 in the body to accommodate the rosette ring. Slidably positioned on the horizontal end connector is a pin 20, which is vertically slidable through a vertical slot 44 and 38 in the connector body. In joining a vertical member to a horizontal member, the rosette 16 is slid into the mouth 18 of the horizontal connector, with an opening 22 in the rosette aligned with the vertical slot 44 and 38 in the end connector. The pin 20 is then rotated upwardly, and then through the vertical slots 44 and 38, which wedges and holds the horizontal member to the vertical member. Collectively, cups and rosettes, or other types of annular members on the vertical scaffold member used to couple to a horizontal end connector will be referred to collectively as annular members.
System scaffolds are used to allow for ease of erection of scaffold platforms. Two scaffold structures, each separately supported by the ground or other supporting surface, can be joined by a walkway or platform extending between the two structures. For long walkways (for instance 10-15 feet), a scaffold truss may be used as the connecting horizontal members to resist bending deformation, such as the sagging of the horizontal, that can result due to the presence of downward directed load forces over the length of the unsupported portion of the of the walkway. A scaffold truss member will have two parallel horizontal scaffold members (a lower and an upper member) with bracing members positioned between and joining the two horizontal members, such has shown in U.S. Pat. No. 5,617,931. For modular or system scaffold systems, the two ends of the truss member will have end connectors positioned thereon (generally on each end of the upper and lower truss horizontal members) that are designed to couple to a vertical scaffold annular member in the modular system. For instance, the horizontal end connector may be the Excel type with a latching connector, where the corresponding vertical connector is an upstanding cup (such as shown in FIG. 1).
Longer scaffold “walkways” can be constructed by connecting two truss members together end-to-end or serially. However, the truss connection between the two truss members has no vertical support, and hence the end-to-end truss joint is subject to compressional forces at top horizontal truss member connection and tensional forces at the bottom horizontal member truss connection, and such truss member connections are normally avoided. Hence, long scaffold walkways (over 10 feet in length) are generally not constructed absent some form of vertical support, such as overhead suspension of the truss member.
A more rigid joint to connect truss members is needed.